Remote plasma based deposition of boron nitride, boron carbide, and boron carbonitride films

ABSTRACT

A boron nitride, boron carbide, or boron carbonitride film can be deposited using a remote plasma chemical vapor deposition (CVD) technique. A boron-containing precursor is provided to a reaction chamber, where the boron-containing precursors has at least one boron atom bonded to a hydrogen atom. Radical species, such as hydrogen radical species, are provided from a remote plasma source and into the reaction chamber at a substantially low energy state or ground state. A hydrocarbon precursor may be flowed along with the boron-containing precursor, and a nitrogen-containing plasma species may be introduced along with the radical species from the remote plasma source and into the reaction chamber. The boron-containing precursor may interact with the radical species along with one or both of the hydrocarbon precursor and the nitrogen-containing precursor to deposit the boron nitride, boron carbide, or boron carbonitride film.

BACKGROUND

The silicon carbide (SiC) class of thin films possesses physical,chemical, electrical, and mechanical properties that can be used in avariety of applications, particularly integrated circuit applications.The boron nitride (B_(x)N_(y)), boron carbide (B_(x)C_(y)), and boroncarbonitride (B_(x)C_(y)N_(z)) class of thin films possesses uniquephysical, chemical, electrical, and mechanical properties that can serveas in a variety of applications, including integrated circuitapplications, and even as an alternative to SiC thin films in somecases.

The background provided herein is for the purposes of generallypresenting the context of the disclosure. Work of the presently namedinventors, to the extent that it is described in this background, aswell as aspects of the description that may not otherwise qualify asprior art at the time of filing, are neither expressly nor impliedlyadmitted as prior art against the present disclosure.

SUMMARY

Provided herein is a method of depositing a boron-containing film on asubstrate. The method includes providing a substrate in a reactionchamber, flowing a boron-containing precursor into the reaction chambertowards the substrate, and flowing a carbon-containing precursor intothe reaction chamber along with the boron-containing precursor. Theboron-containing precursor has one or more B—H bonds. The method furtherincludes generating, from a hydrogen source gas, radicals of hydrogen ina remote plasma source that are generated upstream of theboron-containing precursor and the carbon-containing precursor, andintroducing the radicals of hydrogen into the reaction chamber andtowards the substrate, where the radicals of hydrogen are in a groundstate to react with the boron-containing precursor and thecarbon-containing precursor to form a boron-containing film on thesubstrate.

In some implementations, all or substantially all of the radicals ofhydrogen in an environment adjacent to the substrate are radicals ofhydrogen in the ground state. In some implementations, theboron-containing precursor includes a borane. The boron-containingprecursor can include diborane, triborane, tetraborane, pentaborane,hexaborane, or decaborane. In some implementations, thecarbon-containing precursor is a hydrocarbon molecule with at least acarbon-to-carbon double bond or triple bond. The carbon-containingprecursor can include propylene, ethylene, butene, pentene, butadiene,pentadiene, hexadiene, heptadiene, toluene, benzene, acetylene, propyne,butyne, pentyne, or hexyne. In some implementations, theboron-containing film has no C—C bonds or substantially no C—C bonds. Insome implementations, the method further includes providing anitrogen-containing reactant along with the hydrogen source gas in theremote plasma source, where radicals of the nitrogen-containing reactantare generated in the remote plasma source, and introducing the radicalsof the nitrogen-containing reactant along with the radicals of hydrogeninto the reaction chamber and towards the substrate, where the radicalsof the nitrogen-containing reactant and hydrogen react with theboron-containing precursor and the carbon-containing precursor to form aboron carbonitride (BCN) film. In some implementations, theboron-containing film has a conformality of at least 95%. In someimplementations, the boron-containing film has a Young's modulus equalto or greater than about 130 GPa. In some implementations, theboron-containing precursor has one or more B—C and/or B—N bonds. In someimplementations, an atomic concentration of boron in theboron-containing film is between about 30% and about 75% and an atomicconcentration of carbon in the boron-containing film is between about15% and about 45%.

Another aspect involves a method of depositing a boron-containing filmon a substrate. The method includes providing a substrate in a reactionchamber, flowing a boron-containing precursor into the reaction chambertowards the substrate, generating, from a source gas including ahydrogen gas and a nitrogen-containing reactant, radicals of hydrogenand the nitrogen-containing reactant in a remote plasma source that aregenerated upstream of the boron-containing precursor, and introducingthe radicals of hydrogen and the nitrogen-containing reactant into thereaction chamber and towards the substrate. The radicals of hydrogen arein a ground state to react with the boron-containing precursor to form aboron-containing film on the substrate. The boron-containing precursorhas one or more B—H bonds.

In some implementations, the method further includes flowing acarbon-containing precursor into the reaction chamber along with theboron-containing precursor, where the radicals of hydrogen in the groundstate react with the boron-containing precursor and thecarbon-containing precursor to form the boron-containing film.

These and other aspects are described further below with reference tothe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a cross-sectional schematic of an example boronnitride, boron carbide, or boron carbonitride film deposited over asubstrate.

FIG. 1B illustrates a cross-sectional schematic of an example boronnitride, boron carbide, or boron carbonitride film conformally depositedon features of a substrate.

FIG. 1C illustrates a cross-sectional schematic of example boronnitride, boron carbide, or boron carbonitride vertical structures onsidewalls of a gate electrode of a transistor.

FIG. 1D illustrates a cross-sectional schematic of example boronnitride, boron carbide, or boron carbonitride vertical structures onexposed sidewalls of copper lines in an air gap type metallizationlayer.

FIG. 1E illustrates a cross-sectional schematic of example boronnitride, boron carbide, or boron carbonitride pore sealants for porousdielectric materials.

FIG. 2 shows an example of a chemical reaction between an activatedhydrocarbon molecule from a carbon-containing precursor and an activatedboron-containing precursor.

FIG. 3 illustrates a schematic diagram of an example plasma processingapparatus with a remote plasma source according to some implementations.

FIG. 4 illustrates a schematic diagram of an example plasma processingapparatus with a remote plasma source according to some otherimplementations.

FIG. 5 shows a graph of a FTIR spectrum for remote plasma CVD of a boroncarbonitride film using a boron-containing precursor, carbon-containingprecursor, and remote hydrogen plasma.

FIG. 6 shows graphs of XPS data for B 1 s, C 1 s, and N 1 s for a boroncarbonitride thin film deposited on a substrate.

FIG. 7 shows a TEM image a boron carbonitride thin film deposited onsubstrate features using a boron-containing precursor, carbon-containingprecursor, and remote hydrogen plasma with a carrier gas.

DETAILED DESCRIPTION

In the present disclosure, the terms “semiconductor wafer,” “wafer,”“substrate,” “wafer substrate,” and “partially fabricated integratedcircuit” are used interchangeably. One of ordinary skill in the artwould understand that the term “partially fabricated integrated circuit”can refer to a silicon wafer during any of many stages of integratedcircuit fabrication. A wafer or substrate used in the semiconductordevice industry typically has a diameter of 200 mm, or 300 mm, or 450mm. The following detailed description assumes the present disclosure isimplemented on a wafer. However, the present disclosure is not solimited. The work piece may be of various shapes, sizes, and materials.In addition to semiconductor wafers, other work pieces that may takeadvantage of the present disclosure include various articles such asprinted circuit boards and the like.

Introduction

Manufacture of semiconductor devices typically involves depositing oneor more thin films on a substrate in an integrated fabrication process.For example, the silicon carbide class of thin films may be desirable insemiconductor device fabrication because it has a low dielectricconstant. The silicon carbide class of thin films may also be desirablebecause of its adhesion to other films, electromigration performancewith copper, barrier properties, etch selectivity, low current leakage,high breakdown voltage, conformality, high chemical stability, and highthermal stability, among other properties. However, the performance ofsilicon carbide films may not meet future requirements or demands of themicroelectronics industry.

Boron-containing films including boron nitride (BN), boron carbide (BC),and boron carbonitride (BCN) films may have properties different from ornot present in undoped or doped silicon carbide films. For example,boron nitride, boron carbide, and boron carbonitride thin films may bedesirable in semiconductor device fabrication because of their lowdielectric constant, adhesion to other films, electromigrationperformance with copper, barrier properties, etch selectivity, lowcurrent leakage, high breakdown voltage, conformality, high chemicalstability, and high thermal stability, among other properties. Asdiscussed in more detail below, such boron-containing films may bedeposited with unique physical, chemical, electrical, and mechanicalproperties that may be advantageous over silicon carbide films. As usedherein, boron-containing films may refer to films of boron nitride,boron carbide, or boron carbonitride.

In some aspects of a fabrication process, boron-containing films cantypically be deposited using physical vapor deposition (PVD), chemicalvapor deposition (CVD), or plasma-enhanced chemical vapor deposition(PECVD) processes. Precursor molecules for depositing theboron-containing films include boron-containing molecules such asboranes, higher order boranes, boron halides, aminoboranes, borazines,alkyl-substituted borazines, and the like. The precursor molecules mayreact with a carbon-containing reactant and/or a nitrogen-containingreactant. Depositing high-quality boron-containing films can have manychallenges, such as providing films with excellent step coverage and lowdielectric constant.

Current PECVD processes may use in situ plasma processing in whichplasma is provided directly adjacent to a substrate. While thisdisclosure is not limited by any particular theory, it is believed thatthe plasma conditions in typical PECVD processes cause boron-containingprecursor molecules to form reactive precursor fragments with highsticking coefficients. High sticking coefficients of the precursormolecules and their fragments can deposit boron-containing films withpoor step coverage, as reactive precursor fragments maydisproportionately stick to the upper regions of sidewalls and otherstructures in recessed features.

In addition, direct plasma from current PECVD processes will growcarbon. Specifically, direct plasma conditions will produce energeticspecies that result in C—C, N—N, and/or C—N bonding, in addition to B—Cand B—N bonds, in the boron-containing film. This produces an alloy ofboron carbide and/or boron nitride with carbon and/or carbonitride. Sucha film has poorer mechanical properties and a higher etch rate, whichmay result from the segregation of carbon from boron carbide and/orboron nitride.

Direct plasma conditions sometimes employed in PECVD can lead todirectionality in the deposition because the energy to break up theprecursor molecules can be a low frequency which creates a lot of ionbombardment at the surface. The directional deposition can also lead todeposition of boron-containing films with poor step coverage and lowin-feature sidewall film density. A direct plasma is a plasma in whichthe plasma (electrons and positive ions at an appropriate concentration)reside in close proximity to the substrate surface during deposition,sometimes separated from the substrate surface by only a plasma sheath.

Not only can PECVD conditions result in boron-containing films with poorstep coverage and low in-feature sidewall film density, but PECVDconditions may result in boron-containing films with reduced filmquality and detrimentally high dielectric constants. Direct plasmaconditions may lead to increased boron-hydrogen bonding (B—H) indeposited boron-containing films. Direct plasma conditions may lead toincreased carbon-carbon bonding (C—C), nitrogen-nitrogen bonding (N—N),and/or carbon-nitrogen bonding (C—N). The presence of such bonds canproduce films with low step coverage, poor mechanical properties, andpoor electrical properties, including films with detrimentally highdielectric constants.

Environment at the Substrate Surface During Deposition

FIG. 1A illustrates a cross-sectional schematic of an example boronnitride, boron carbide, or boron carbonitride film deposited over asubstrate. A boron-containing film 101 in FIG. 1A can be a boronnitride, boron carbide, or boron carbonitride film. The boron-containingfilm 101 can be formed under process conditions producing a relativelymild environment adjacent to the substrate 100. The substrate 100 can beany wafer, semiconductor wafer, partially fabricated integrated circuit,printed circuit board, display screen, or other appropriate work piece.The process for depositing the boron-containing film 101 can involve oneor more boron-containing precursors each having one or more B—H bonds.At least one of the boron atoms is bonded to a hydrogen atom. In someimplementations, each of the boron-containing precursors can have one ormore B—B bonds. In some implementations, each of the boron-containingprecursors has no B—C bonds or B—N bonds. The chemical structures ofexample boron-containing precursors are discussed in further detailbelow.

The boron-containing precursor includes one or more B—H bonds andoptionally one or more B—B bonds. However, it will be understood thatadditional boron-containing precursors (e.g., boron trichloride) may notnecessarily include B—H bonds or B—B bonds. These additionalboron-containing precursors may be provided concurrently with theboron-containing precursor having one or more B—H bonds. During thedeposition process, the B—H bonds are selectively broken and serve asactive sites for cross-linking or forming bonds with other reactants. Inother words, the reaction conditions adjacent to the substrate 100provide for the selective breaking of B—H bonds so that hydrogen isextracted from the broken B—H bonds.

Generally, the described reaction conditions exist at the exposed faceof the substrate 100 (the face where the boron-containing film 101 isdeposited). They may further exist at some distance above the substrate100, e.g., about 0.5 micrometers to about 150 millimeters above thesubstrate 100. In effect, activation of the precursor can happen in thegas phase at a substantial distance above the substrate 100. Typically,the pertinent reaction conditions will be uniform or substantiallyuniform over the entire exposed face of the substrate 100, althoughcertain applications may permit some variation.

In addition to boron-containing precursors, the environment adjacent thework piece (e.g., substrate 100) includes one or more radical species,preferably in a substantially low energy state. An example of suchspecies includes hydrogen radicals (i.e., hydrogen atom radicals). Insome embodiments, all, or substantially all, or a substantial fractionof the hydrogen atom radicals can be in the ground state, e.g., at leastabout 90% or 95% of the hydrogen atom radicals adjacent the work pieceare in the ground state. In certain embodiments, a source gas isintroduced into the remote plasma source, where the source gas can be ahydrogen source gas. In some embodiments, the source gas is provided ina carrier gas such as helium. As an example, hydrogen gas (H₂) may beprovided in a helium carrier at a concentration of about 1-10% hydrogen.Pressure, fraction of carrier gas such as helium, and other processconditions are chosen so that the hydrogen atoms encounter the substrate100 as radicals in a low energy state without recombining.

As explained elsewhere, hydrogen gas may be supplied into a remoteplasma source to generate the hydrogen atom radicals. The remote plasmasource may be positioned upstream from the substrate 100 and theenvironment adjacent to the substrate 100. Once generated, the hydrogenatom radicals may be in an excited energy state. For example, hydrogenin an excited energy state can have an energy of at least 10.2 eV (firstexcited state). In some implementations, when the excited hydrogen atomradicals lose their energy, or relax, the excited hydrogen atom radicalmay become a substantially low energy state hydrogen atom radical or aground state hydrogen atom radical. In some implementations, thedeposition conditions may be designed so that the excited hydrogen atomradicals lose energy or relax to form substantially low energy state orground state hydrogen atom radicals. For example, the remote plasmasource or associated components may be designed so that a residence timeof hydrogen atom radicals diffusing from the remote plasma source to thesubstrate 100 is greater than the energetic relaxation time of anexcited hydrogen atom radical. The energetic relaxation time for anexcited hydrogen atom radical can be about equal to or less than about1×10⁻³ seconds.

A state in which a substantial fraction of hydrogen atom radicals are inthe ground state can be achieved by various techniques. Someapparatuses, such as described below, are designed to achieve thisstate. Apparatus features and process control features can be tested andtuned to produce a mild state in which a substantial fraction of thehydrogen atom radicals are in the ground state. For example, anapparatus may be operated and tested for charged particles downstream ofthe plasma source; i.e., near the substrate 100. The process andapparatus may be tuned until substantially no charged species exist nearthe substrate 100. Additionally, apparatus and process features may betuned to a configuration where they begin to produce a boron-containingfilm 101 from a boron-containing precursor. The relatively mildconditions that support such film deposition are chosen.

In addition to boron-containing precursors, the environment adjacent tothe work piece (e.g., substrate 100) can include one or morenitrogen-containing radical species (i.e., nitrogen-containing plasmaspecies). The nitrogen-containing radical species may incorporatenitrogen in the boron-containing film 101 to form a boron nitride filmor boron carbonitride film. In some implementations, thenitrogen-containing radical species may include elemental nitrogenradicals (atomic or diatomic) and/or N—H containing radicals such asammonia radicals. Examples of N—H containing radicals include but arenot limited to radicals of methylamine, dimethylamine, and aniline.

The nitrogen-containing radical species and the hydrogen radical speciesmay be generated by a remote plasma source. The remote plasma source maybe positioned upstream from the substrate 100 and the environmentadjacent to the substrate 100. Accordingly, the nitrogen-containingradical species may be introduced to a reaction chamber and towards thesubstrate 100 along the same flow path as the hydrogen radical species.A source gas can be introduced into the remote plasma source, where thesource gas can include hydrogen gas, nitrogen gas, N—H containingspecies, or mixtures thereof. The aforementioned radical species may begenerated from the source gas. The hydrogen gas is at least partiallyconverted to ions and/or radicals of hydrogen in the remote plasmasource. A nitrogen-containing reactant such as nitrogen gas (N₂) orammonia (NH₃) is provided to the remote plasma source, where thenitrogen-containing reactant is at least partially converted to ionsand/or radicals of the nitrogen-containing reactant in the remote plasmasource. This generates the nitrogen-containing radicals in the remoteplasma source. Nitrogen-containing radical species and hydrogen radicalspecies both react with the boron-containing precursor(s) to produce thedeposited boron-containing film 101.

In addition to boron-containing precursors, the environment adjacent tothe work piece (e.g., substrate 100) can include one or morecarbon-containing precursors. The carbon-containing precursors mayincorporate carbon in the boron-containing film 101 to form a boroncarbide film or boron carbonitride film. Each of the carbon-containingprecursors may be a hydrocarbon molecule with one or morecarbon-to-carbon double bonds or triple bonds. The carbon-containingprecursors are flowed along with the boron-containing precursors intothe reaction chamber towards the substrate 100.

The carbon-containing precursors are introduced into the reactionchamber downstream from the remote plasma source. Put another way, thehydrogen radical species and/or nitrogen-containing radical species aregenerated upstream from the carbon-containing precursors and theboron-containing precursors. The carbon-containing precursors may beintroduced to the reaction chamber via the same flow path as theboron-containing precursors. This means that the carbon-containingprecursors and the boron-containing precursors may be introduced via agas outlet or showerhead without direct exposure to plasma.

In addition to boron-containing precursors, the environment adjacent tothe work piece (e.g., substrate 100) can include an inert carrier gas ordiluent gas. Examples of an inert carrier gas or diluent gas include butare not limited to helium (He), neon (Ne), argon (Ar), krypton (Kr),xenon (Xe), and nitrogen (N₂). Upstream from the deposition reactionsurface, the boron-containing precursors can be mixed with the inertcarrier gas. In some implementations, the hydrogen gas is provided withan inert carrier gas of helium. The inert carrier gas can be providedwith a mass greater than the hydrogen gas. In some implementations, agas mixture of helium, hydrogen, and nitrogen is provided in the remoteplasma source.

The temperature in the environment adjacent to the substrate 100 can beany suitable temperature facilitating the deposition reaction, butsometimes limited by the application of the device containing theboron-containing film 101. In some embodiments, the temperature in theenvironment adjacent to the substrate 100 can be largely controlled bythe temperature of a pedestal on which a substrate 100 is supportedduring deposition of the boron-containing film 101. In some embodiments,the operating temperature can be between about 50° C. and about 500° C.For example, the operating temperature can be between about 250° C. andabout 400° C. in many integrated circuit applications. In someembodiments, increasing the temperature can lead to increasedcross-linking on the substrate surface.

The pressure in the environment adjacent to the substrate 100 can be anysuitable pressure to produce reactive radicals in a reaction chamber. Insome embodiments, the pressure can be about 35 Torr or lower. Forexample, the pressure can be between about 10 Torr and about 20 Torr,such as in embodiments implementing a microwave generated plasma. Inother examples, the pressure can be less than about 5 Torr, or betweenabout 0.2 Torr and about 5 Torr, such as in embodiments implementing aradio-frequency (RF) generated plasma.

The environment adjacent to the substrate 100 provides for deposition ofthe boron-containing film 101 on the substrate 100 by remote plasma CVD.A boron-containing precursor molecule may be flowed into a reactionchamber towards the substrate 100. A source gas is supplied to a remoteplasma source upstream from the reaction chamber, and power is providedto the remote plasma source that may cause the source gas to dissociateand generate ions and radicals in an excited energy state. Afterexcitation, the radicals in the excited energy state relax tosubstantially low energy state radicals or ground state radicals, suchas ground state hydrogen radicals. In some embodiments, the source gasmay include a nitrogen-containing reactant so that excitednitrogen-containing plasma species may be generated in the remote plasmasource. The radical species of the source gas may react with bonds inthe boron-containing precursor molecule, where the boron-containingprecursor molecule has at least one B—H bond. The reaction may occur atthe environment adjacent to the substrate 100 to cause deposition of theboron-containing film 101, which may be a boron nitride or boroncarbonitride film. In some embodiments, a carbon-containing precursormolecule may be flowed into the reaction chamber along with theboron-containing precursor molecule. The radical species of the sourcegas may react with bonds in the carbon-containing precursor molecule andthe boron-containing precursor molecule. The reaction may occur at theenvironment adjacent to the substrate 100 to cause deposition of theboron-containing film 101, which may be a boron carbide or boroncarbonitride film.

In some embodiments, substantially all or a substantial fraction ofatoms of the deposited film are provided by the precursor molecules,including the boron-containing precursor molecules and carbon-containingprecursor molecules, and the nitrogen-containing reactant. In suchcases, the low energy radicals including the ground state hydrogenradicals used to drive the deposition reaction do not substantiallycontribute to the mass of the deposited layer. In some embodiments, someradicals of higher energy state or even ions can potentially be presentnear the wafer plane.

In some embodiments, the process conditions employ radical species in asubstantially low energy state sufficient to activate carbon-containingprecursor molecules and boron-containing precursor molecules. Suchprocess conditions may not have substantial amounts of ions, electrons,or radical species in high energy states such as states above the groundstate. In some embodiments, the concentration of ions in the regionadjacent the film is no greater than about 10⁷/cm³. The presence ofsubstantial amounts of ions or high energy radicals may tend to producefilms with undesirable electrical properties (e.g., high dielectricconstants and/or low breakdown voltages), mechanical properties (e.g.,low Young's modulus and/or high intrinsic stress), and poorconformality.

FIG. 2 shows an example of a chemical reaction between an activatedhydrocarbon molecule from a carbon-containing precursor and an activatedboron-containing precursor. Without being limited by any theory, thehydrogen radicals in the substantially low energy state or ground statemay interact with alkyne or alkene groups in the hydrocarbon moleculethat results in the formation of activated hydrocarbon molecules. Inaddition, the hydrogen radicals in the substantially low energy state orground state may interact with the B—H bond(s) in the boron-containingprecursor that results in the formation of activated boron-containingprecursors. The hydrogen radicals activate the double or triple bonds inthe hydrocarbon molecule in a process called “saturation” to generate acarbon-based radical species. Furthermore, the hydrogen radicals mayreact with the B—H bond(s) in the boron-containing precursor to breakthe B—H bond(s) and form a boron-based radical species and hydrogen (H₂)byproduct. In some instances, the boron-based radical species can reactwith the double or triple bond in the hydrocarbon molecule to form B—Cbonds and deposit a boron-containing film. In some instances, thecarbon-based radical species reacts with a weak B—H bond in theboron-containing precursor to form a B—C bond and a hydrogen (H●)radical, where the reaction results in the deposition of aboron-containing film.

In addition or in the alternative to the carbon-containing precursor,nitrogen-based plasma species from the nitrogen-containing reactant mayparticipate in a deposition reaction to incorporate nitrogen in theboron-containing film. Examples of nitrogen-based plasma species mayinclude N—H containing radicals or nitrogen radicals. The nitrogen-basedplasma species may break B—H bond(s) to form B—N bond(s) and deposit aboron nitride or boron carbonitride film.

In some embodiments, only the radical species, the boron-containingprecursors, and the carbon-containing precursors contribute to thecomposition of the deposited boron-containing film. In otherembodiments, the deposition reaction includes a co-reactant other thanthe aforementioned precursors and the radical species, which may or maynot contribute to the composition of the boron-containing film. Examplesof such co-reactants include carbon dioxide (CO₂), carbon monoxide (CO),water (H₂O), methanol (CH₃OH), oxygen (O₂), ozone (O₃), nitrous oxide(N₂O), and combinations thereof. Such materials may be used as nitridingagents, oxidizers, reductants, etc. In some cases, they can be used totune an amount of carbon in the deposited film. In some cases, they canbe used to tune an amount of nitrogen or oxygen in the deposited film.In some implementations, the co-reactant may be introduced along withthe boron-containing precursor; e.g., without direct exposure to plasma.In some implementations, the co-reactant may be introduced along withthe hydrogen radical species; e.g., with exposure to plasma in a remoteplasma source.

Boron-containing films may be used in semiconductor devices. Forexample, boron nitride, boron carbide, or boron carbonitride films maybe employed as metal diffusion barriers, etch stop layers, hard masklayers, gate spacers for source and drain implants, encapsulationbarriers for magnetoresistive random-access memory (MRAM) or resistiverandom-access memory (RRAM), and hermetic diffusion barriers at airgaps, among other applications. FIGS. 1B-1E illustrate cross-sections ofstructures containing boron-containing films in a variety ofapplications. FIG. 1B illustrates a cross-sectional schematic of anexample boron nitride, boron carbide, or boron carbonitride filmconformally deposited on features of a substrate. FIG. 1C illustrates across-sectional schematic of example boron nitride, boron carbide, orboron carbonitride vertical structures on sidewalls of a gate electrodeof a transistor. FIG. 1D illustrates a cross-sectional schematic ofexample boron nitride, boron carbide, or boron carbonitride verticalstructures on exposed sidewalls of copper lines in an air gap typemetallization layer. FIG. 1E illustrates a cross-sectional schematic ofexample boron nitride, boron carbide, or boron carbonitride poresealants for porous dielectric materials. Each of these applications isdiscussed in further detail below.

Chemical Structure of Precursors

As discussed, at least some of the precursors employed in forming boronnitride, boron carbide, or boron carbonitride films can includeboron-containing precursors having one or more B—H bonds. In someembodiments, the boron-containing precursors have no B—N bonds or B—Cbonds. In other words, the boron-containing precursors do not havenitrogen or carbon built into the precursors in forming a carbide ornitride film. In some embodiments, the boron-containing precursor hasone or more B—B bonds.

The boron-containing precursor can be a borane precursor generallyhaving a chemical formula B_(x)H_(y). In some embodiments, the boraneprecursor is borane (BH₃). In some embodiments, the borane precursor isdiborane (B₂H₆). In some embodiments, the borane precursor is a higherorder borane such as triborane (B₃H₇), tetraborane (B₄H₁₀), pentaborane(B₅H₉), hexaborane (B₆H₁₀), and decaborane (B₁₀H₁₄).

Boranes may form stable complexes such as borane amine complexes. Forexample, a borane amine complex may include dimethylamineborane complex((CH₃)₂NH:BH₃). The borane amine complex may generally have the chemicalformula NR₃:BH₃, where R can be any combination of H or alkyl, allyl,alkenyl, alkynyl, alkylaryl, arylalkyl, phenyl, alkene, and alkyneligands.

In some implementations, the boron-containing precursor can be aborazine generally having a chemical formula B_(x)H_(y)N_(z). Forexample, a borazine precursor can have the chemical formula B₃H₆N₃.

Where the deposited boron-containing film is a boron carbide or boroncarbonitride film, at least some of the precursors employed in thedeposition reaction can include a carbon-containing precursor. Thecarbon-containing precursor can be any suitable hydrocarbon molecule. Insome embodiments, the hydrocarbon molecule includes a carbon chainbetween 3 carbon atoms and 7 carbon atoms. In some embodiments, thehydrocarbon molecule may include one or more unsaturated carbon bonds,such as one or more carbon-to-carbon double bonds or triple bonds. Thus,the hydrocarbon molecule may include an alkene or alkyne group. Examplesof suitable hydrocarbon molecules include propylene, ethylene, butene,pentene, butadiene, pentadiene (e.g., 1,4 pentadiene), hexadiene,hexadiene, heptadiene, toluene, and benzene. Additional examples ofsuitable hydrocarbon molecules include acetylene, propyne, butyne,pentyne (e.g., 1-pentyne), and hexyne (e.g., 2-hexyne).

In some embodiments, the carbon-containing precursor may be a depositingadditive. A depositing additive may form species with theboron-containing precursor regardless of temperature, even fortemperatures greater than about 50° C. or greater than about 25° C. Thecarbon-containing precursor does not serve as a passive spectator, butcan significantly contribute to the composition of the boron-containingfilm. The carbon-containing precursor and byproducts of any reactionwith the hydrogen radicals in the substantially low energy state orground state may get incorporated in the boron-containing film in asubstantial amount. As used herein, a “substantial amount” with respectto incorporation of the carbon from the carbon-containing precursor inthe boron-containing film may refer to a change in atomic concentrationof carbon by an amount equal to or greater than about 5% compared todeposition of the boron-containing film without the carbon-containingprecursor.

Apparatus

One aspect of the disclosure is an apparatus configured to accomplishthe methods described herein. A suitable apparatus includes hardware foraccomplishing the process operations and a system controller havinginstructions for controlling process operations in accordance with thepresent disclosure. In some embodiments, the apparatus for performingthe aforementioned process operations can include a remote plasmasource. A remote plasma source provides mild reaction conditions incomparison to a direct plasma. An example of a suitable remote plasmaapparatus is described in U.S. patent application Ser. No. 14/062,648,filed Oct. 24, 2013, which is incorporated herein by reference in itsentirety and for all purposes.

FIG. 3 presents a schematic diagram of a remote plasma apparatusaccording to certain embodiments. The device 300 includes a reactionchamber 310 with a showerhead 320. Inside the reaction chamber 310, asubstrate 330 rests on a stage or pedestal 335. In some embodiments, thepedestal 335 can be fitted with a heating/cooling element. A controller340 may be connected to the components of the device 300 to control theoperation of the device 300. For example, the controller 340 may containinstructions for controlling process conditions for the operations ofthe device 300, such as the temperature process conditions and/or thepressure process conditions. In some embodiments, the controller 340 maycontain instructions for controlling the flow rates of precursor gas,co-reactant gas, source gas, and carrier gas. The controller 340 maycontain instructions for changing the flow rate of the co-reactant gasover time. In addition or in the alternative, the controller 340 maycontain instructions for changing the flow rate of the precursor gasover time. A more detailed description of the controller 340 is providedbelow.

During operation, gases or gas mixtures are introduced into the reactionchamber 310 via one or more gas inlets coupled to the reaction chamber310. In some embodiments, two or more gas inlets are coupled to thereaction chamber 310. A first gas inlet 355 can be coupled to thereaction chamber 310 and connected to a vessel 350, and a second gasinlet 365 can be coupled to the reaction chamber 310 and connected to aremote plasma source 360. In embodiments including remote plasmaconfigurations, the delivery lines for the precursors and the radicalspecies generated in the remote plasma source are separated. Hence, theprecursors and the radical species do not substantially interact beforereaching the substrate 330. It will be understood that in someimplementations the gas lines may be reversed so that the vessel 350 mayprovide precursor gas flow through the second gas inlet 365 and theremote plasma source 360 may provide ions and radicals through the firstgas inlet 355.

One or more radical species may be generated in the remote plasma source360 and configured to enter the reaction chamber 310 via the gas secondinlet 365. Any type of plasma source may be used in remote plasma source360 to create the radical species. This includes, but is not limited to,capacitively coupled plasmas, inductively coupled plasmas, microwaveplasmas, DC plasmas, and laser-created plasmas. An example of acapacitively coupled plasma can be a radio frequency (RF) plasma. Ahigh-frequency plasma can be configured to operate at 13.56 MHz orhigher. An example of such a remote plasma source 360 can be the GAMMA®,manufactured by Lam Research Corporation of Fremont, Calif. Anotherexample of such a RF remote plasma source 360 can be the Astron®,manufactured by MKS Instruments of Wilmington, Mass., which can beoperated at 440 kHz and can be provided as a subunit bolted onto alarger apparatus for processing one or more substrates in parallel. Insome embodiments, a microwave plasma can be used as the remote plasmasource 360, such as the Astex®, also manufactured by MKS Instruments. Amicrowave plasma can be configured to operate at a frequency of 2.45GHz. Gas provided to the remote plasma source may include hydrogen,nitrogen, oxygen, and other gases as mentioned elsewhere herein. Incertain embodiments, hydrogen is provided in a carrier such helium. Asan example, hydrogen gas may be provided in a helium carrier at aconcentration of about 1-10% hydrogen.

The precursors can be provided in vessel 350 and can be supplied to theshowerhead 320 via the first gas inlet 355. The showerhead 320distributes the precursors into the reaction chamber 310 toward thesubstrate 330. The substrate 330 can be located beneath the showerhead320. It will be appreciated that the showerhead 320 can have anysuitable shape, and may have any number and arrangement of ports fordistributing gases to the substrate 330. The precursors can be suppliedto the showerhead 320 and ultimately to the substrate 330 at acontrolled flow rate.

The one or more radical species formed in the remote plasma source 360can be carried in the gas phase toward the substrate 330. The one ormore radical species can flow through a second gas inlet 365 into thereaction chamber 310. It will be understood that the second gas inlet365 need not be transverse to the surface of the substrate 330 asillustrated in FIG. 3. In certain embodiments, the second gas inlet 365can be directly above the substrate 330 or in other locations. Thedistance between the remote plasma source 360 and the reaction chamber310 can be configured to provide mild reactive conditions such that theionized species generated in the remote plasma source 360 aresubstantially neutralized, but at least some radical species insubstantially low energy states remain in the environment adjacent tothe substrate 330. Such low energy state radical species are notrecombined to form stable compounds. The distance between the remoteplasma source 360 and the reaction chamber 310 can be a function of theaggressiveness of the plasma (e.g., determined in part by the source RFpower level), the density of gas in the plasma (e.g., if there's a highconcentration of hydrogen atoms, a significant fraction of them mayrecombine to form H₂ before reaching the reaction chamber 310), andother factors. In some embodiments, the distance between the remoteplasma source 360 and the reaction chamber 310 can be between about 1 cmand 30 cm, such as about 5 cm or about 15 cm.

In some embodiments, a carbon-containing precursor, which is not theprimary boron-containing precursor or a hydrogen radical, is introducedduring the deposition reaction. In some implementations, the apparatusis configured to introduce the nitrogen-containing plasma speciesthrough the second gas inlet 365, in which case the nitrogen-containingreactant is at least partially converted to plasma. In someimplementations, the apparatus is configured to introduce thecarbon-containing precursor through the showerhead 320 via the first gasinlet 355.

FIG. 4 illustrates a schematic diagram of an example plasma processingapparatus with a remote plasma source according to some otherimplementations. The plasma processing apparatus 400 includes the remoteplasma source 402 separated from a reaction chamber 404. The remoteplasma source 402 is fluidly coupled with the reaction chamber 404 via amultiport gas distributor 406, which may also be referred to as ashowerhead. Radical species are generated in the remote plasma source402 and supplied to the reaction chamber 404. One or moreboron-containing precursors are supplied to the reaction chamber 404downstream from the remote plasma source 402 and from the multiport gasdistributor 406. The one or more boron-containing precursors react withthe radical species in a chemical vapor deposition zone 408 of thereaction chamber 404 to deposit a boron-containing film on a surface ofa substrate 412. The chemical vapor deposition zone 408 includes anenvironment adjacent to the surface of the substrate 412.

The substrate 412 is supported on a substrate support or pedestal 414.The pedestal 414 may move within the reaction chamber 404 to positionthe substrate 412 within the chemical vapor deposition zone 408. In theembodiment shown in FIG. 4, pedestal 414 is shown having elevated thesubstrate 410 within the chemical vapor deposition zone 408. Thepedestal 414 may also adjust the temperature of the substrate 412 insome embodiments, which can provide some selective control overthermally activated surface reactions on the substrate 412.

FIG. 4 shows a coil 418 arranged around the remote plasma source 402,where the remote plasma source 402 includes an outer wall (e.g., quartzdome). The coil 418 is electrically coupled to a plasma generatorcontroller 422, which may be used to form and sustain plasma within aplasma region 424 via inductively coupled plasma generation. In someimplementations, the plasma generator controller 422 may include a powersupply for supplying power to the coil 418, where the power can be in arange between about 1 and 6 kilowatts (kW) during plasma generation. Insome implementations, electrodes or antenna for parallel plate orcapacitively coupled plasma generation may be used to generate acontinuous supply of radicals via plasma excitation rather thaninductively coupled plasma generation. Regardless of the mechanism usedto ignite and sustain the plasma in the plasma region 424, radicalspecies may continuously be generated using plasma excitation duringfilm deposition. In some implementations, hydrogen radicals aregenerated under approximately steady-state conditions duringsteady-state film deposition, though transients may occur at thebeginning and end of film deposition.

A supply of hydrogen radicals may be continuously generated within theplasma region 424 while hydrogen gas or other source gas is beingsupplied to the remote plasma source 402. Excited hydrogen radicals maybe generated in the remote plasma source 402. If not re-excited orre-supplied with energy, or re-combined with other radicals, the excitedhydrogen radicals lose their energy, or relax. Thus, excited hydrogenradicals may relax to form hydrogen radicals in a substantially lowenergy state or ground state.

The hydrogen gas or other source gas may be diluted with one or moreadditional gases. These one or more additional gases may be supplied tothe remote plasma source 402. In some implementations, the hydrogen gasor other source gas is mixed with one or more additional gases to form agas mixture, where the one or more additional gases can include acarrier gas. Non-limiting examples of additional gases can includehelium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), andnitrogen (N₂). The one or more additional gases may support or stabilizesteady-state plasma conditions within the remote plasma source 402 oraid in transient plasma ignition or extinction processes. In someimplementations, diluting hydrogen gas or other source gas with helium,for example, may permit higher total pressures without concomitantplasma breakdown. Put another way, a dilute gas mixture of hydrogen gasand helium may permit higher total gas pressure without increasingplasma power to the remote plasma source 402. As shown in FIG. 4, asource gas supply 426 is fluidly coupled with the remote plasma source402 for supplying the hydrogen gas or source gas. In addition, anadditional gas supply 428 is fluidly coupled with the remote plasmasource 402 for supplying the one or more additional gases. The one ormore additional gases may also include a co-reactant gas as describedabove. While the embodiment in FIG. 4 depicts the gas mixture of thesource gas and the one or more additional gases being introduced throughseparate gas outlets, it will be understood that the gas mixture may beintroduced directly into the remote plasma source 402. That is, apre-mixed dilute gas mixture may be supplied to the remote plasma source402 through a single gas outlet.

Gases, such as excited hydrogen and helium radicals and relaxedgases/radicals, flow out of the remote plasma source 402 and into thereaction chamber 404 via multiport gas distributor 406. Gases within themultiport gas distributor 406 and within the reaction chamber 404 aregenerally not subject to continued plasma excitation therein. In someimplementations, the multiport gas distributor 406 includes an ionfilter and/or a photon filter. Filtering ions and/or photons may reducesubstrate damage, undesirable re-excitation of molecules, and/orselective breakdown or decomposition of boron-containing precursorswithin the reaction chamber 404. Multiport gas distributor 406 may havea plurality of gas ports 434 to diffuse the flow of gases into thereaction chamber 404. In some implementations, the plurality of gasports 434 may be mutually spaced apart. In some implementations, theplurality of gas ports 434 may be arranged as an array of regularlyspaced apart channels or through-holes extending through a plateseparating the remote plasma source 402 and the reaction chamber 404.The plurality of gas ports 434 may smoothly disperse and diffuse exitingradicals from the remote plasma source 402 into the reaction chamber404.

Typical remote plasma sources are far removed from reaction vessels.Consequently, radical extinction and recombination, e.g., via wallcollision events, may reduce active species substantially. In contrast,in some implementations, dimensions for the plurality of gas ports 434may be configured in view of the mean free path or gas flow residencetime under typical processing conditions to aid the free passage ofradicals into the reaction chamber 404. In some implementations,openings for the plurality of gas ports 434 may occupy between about 5%and about 20% of an exposed surface area of the multiport gasdistributor 406. In some implementations, the plurality of gas ports 434may each have an axial length to diameter ratio of between about 3:1 and10:1 or between about 6:1 and about 8:1. Such aspect ratios may reducewall-collision frequency for radical species passing through theplurality of gas ports 434 while providing sufficient time for amajority of excited state radical species to relax to ground stateradical species. In some implementations, dimensions of the plurality ofgas ports 434 may be configured so that the residence time of gasespassing through the multiport gas distributor 406 is greater than thetypical energetic relaxation time of an excited state radical species.Excited state radical species for hydrogen source gas may be denoted byθH* in FIG. 4 and ground state radical species for hydrogen source gasmay be denoted by θH in FIG. 4.

In some implementations, excited state radical species exiting theplurality of gas ports 434 may flow into a relaxation zone 438 containedwithin an interior of the reaction chamber 404. The relaxation zone 438is positioned upstream of the chemical vapor deposition zone 408 butdownstream of the multiport gas distributor 406. Substantially all or atleast 90% of the excited state radical species exiting the multiport gasdistributor 406 will transition into relaxed state radical species inthe relaxation zone 438. Put another way, almost all of the excitedstate radical species (e.g., excited hydrogen radicals) entering therelaxation zone 438 become de-excited or transition into a relaxed stateradical species (e.g., ground state hydrogen radicals) before exitingthe relaxation zone 438. In some implementations, process conditions ora geometry of the relaxation zone 438 may be configured so that theresidence time of radical species flowing through the relaxation zone438, e.g., a time determined by mean free path and mean molecularvelocity, results in relaxed state radical species flowing out of therelaxation zone 438.

With the delivery of radical species to the relaxation zone 438 from themultiport gas distributor 406, one or more boron-containing precursorsand/or one or more carbon-containing precursors may be introduced intothe chemical vapor deposition zone 408. The one or more boron-containingprecursors may be introduced via a gas distributor or gas outlet 442,where the gas outlet 442 may be fluidly coupled with a precursor supplysource 440. The relaxation zone 438 may be contained within a spacebetween the multiport gas distributor 406 and the gas outlet 442. Thegas outlet 442 may include mutually spaced apart openings so that theflow of the one or more boron-containing precursors may be introduced ina direction parallel with gas mixture flowing from the relaxation zone438. The gas outlet 442 may be located downstream from the multiport gasdistributor 406 and the relaxation zone 438. The gas outlet 442 may belocated upstream from the chemical vapor deposition zone 408 and thesubstrate 412. The chemical vapor deposition zone 408 is located withinthe interior of the reaction chamber 404 and between the gas outlet 442and the substrate 412.

Substantially all of the flow of the one or more boron-containingprecursors may be prevented from mixing with excited state radicalspecies adjacent to the multiport gas distributor 406. Relaxed or groundstate radical species mix in a region adjacent to the substrate 412 withthe one or more boron-containing precursors. The chemical vapordeposition zone 408 includes the region adjacent to the substrate 412where the relaxed or ground state radical species mix with the one ormore boron-containing precursors. The relaxed or ground state radicalspecies mix with the one or more boron-containing precursors in the gasphase during CVD formation of a boron-containing film.

In some implementations, a carbon-containing precursor may be introducedfrom the gas outlet 442 and flowed along with the one or moreboron-containing precursors. The carbon-containing precursor may beintroduced downstream from the remote plasma source 402. Thecarbon-containing precursor may be supplied from the precursor supplysource 440 or other source (not shown) fluidly coupled to the gas outlet442. The carbon-containing precursor may be a hydrocarbon molecule withone or more carbon-to-carbon double bonds or triple bonds. In someimplementations, a nitrogen-containing plasma species may be introducedfrom the multiport gas distributor 406 and flowed along with thehydrogen radical species generated in the remote plasma source 402 andinto the reaction chamber 404. This may include radicals and/or ions ofa nitrogen-containing reactant provided in the remote plasma source 402.The nitrogen-containing reactant or any other co-reactant may besupplied from the additional gas supply 428.

The gas outlet 442 may be separated from the multiport gas distributor406 by a sufficient distance to prevent back diffusion or back streamingof the one or more boron-containing precursors. In some implementations,the gas outlet 442 may be separated from the plurality of gas ports 434by a distance between about 0.5 inches and about 5 inches, or betweenabout 1.5 inches and about 4.5 inches, or between about 1.5 inches andabout 3 inches.

Process gases may be removed from the reaction chamber 404 via an outlet448 configured that is fluidly coupled to a pump (not shown). Thus,excess boron-containing precursors, carbon-containing precursors,radical species, and diluent and displacement or purge gases may beremoved from the reaction chamber 404. In some implementations, a systemcontroller 450 is in operative communication with the plasma processingapparatus 400. In some implementations, the system controller 450includes a processor system 452 (e.g., microprocessor) configured toexecute instructions held in a data system 454 (e.g., memory). In someimplementations, the system controller 450 may be in communication withthe plasma generator controller 422 to control plasma parameters and/orconditions. In some implementations, the system controller 450 may be incommunication with the pedestal 414 to control pedestal elevation andtemperature. In some implementations, the system controller 450 maycontrol other processing conditions, such as RF power settings,frequency settings, duty cycles, pulse times, pressure within thereaction chamber 404, pressure within the remote plasma source 402, gasflow rates from the source gas supply 426 and the additional gas supply428, gas flow rates from the precursor supply source 440 and othersources, temperature of the pedestal 414, and temperature of thereaction chamber 404, among others.

Aspects of the controller 450 of FIG. 4 described below also apply tothe controller 340 of FIG. 3. The controller 450 may containinstructions for controlling process conditions for the operation of theplasma processing apparatus 400. The controller 450 will typicallyinclude one or more memory devices and one or more processors. Theprocessor may include a CPU or computer, analog and/or digitalinput/output connections, stepper motor controller boards, etc.Instructions for implementing appropriate control operations areexecuted on the processor. These instructions may be stored on thememory devices associated with the controller 450 or they may beprovided over a network.

In certain embodiments, the controller 450 controls all or mostactivities of the plasma processing apparatus 400 described herein. Forexample, the controller 450 may control all or most activities of theplasma processing apparatus 400 associated with depositing aboron-containing film and, optionally, other operations in a fabricationflow that includes the boron-containing film. The controller 450 mayexecute system control software including sets of instructions forcontrolling the timing, gas composition, gas flow rates, chamberpressure, chamber temperature, RF power levels, substrate position,and/or other parameters. Other computer programs, scripts, or routinesstored on memory devices associated with the controller 450 may beemployed in some embodiments. To provide relatively mild reactiveconditions at the environment adjacent to the substrate 412, parameterssuch as the RF power levels, gas flow rates to the plasma region 424,gas flow rates to the chemical vapor deposition zone 408, and timing ofthe plasma ignition can be adjusted and maintained by controller 450.Additionally, adjusting the substrate position may further reduce thepresence of high-energy radical species at the environment adjacent tothe substrate 412. In a multi-station reactor, the controller 450 maycomprise different or identical instructions for different apparatusstations, thus allowing the apparatus stations to operate eitherindependently or synchronously.

In some embodiments, the controller 450 may include instructions forperforming operations such as flowing one or more boron-containingprecursors through the gas outlet 442 into the reaction chamber 404,providing a source gas into the remote plasma source 402, generating oneor more radical species of the source gas in the remote plasma source402, introducing the one or more radical species in a substantially lowenergy state from the remote plasma source 402 into the reaction chamber404 to react with the one or more boron-containing precursors to deposita boron-containing film on the substrate 412. The one or more radicalspecies in the reaction chamber 404 in an environment adjacent to thesubstrate 412 may be hydrogen radicals in a ground state. In someimplementations, the controller 450 may include instructions for flowinga carbon-containing precursor with the one or more boron-containingprecursors into the reaction chamber 404. In some implementations, thesource gas can include a nitrogen-containing reactant such as nitrogengas or ammonia.

In some embodiments, the apparatus 400 may include a user interfaceassociated with controller 450. The user interface may include a displayscreen, graphical software displays of the apparatus 400 and/or processconditions, and user input devices such as pointing devices, keyboards,touch screens, microphones, etc.

The computer program code for controlling the above operations can bewritten in any conventional computer readable programming language: forexample, assembly language, C, C++, Pascal, Fortran, or others. Compiledobject code or script is executed by the processor to perform the tasksidentified in the program.

Signals for monitoring the process may be provided by analog and/ordigital input connections of the system controller. The signals forcontrolling the process are output on the analog and digital outputconnections of the processing system.

In general, the methods described herein can be performed on systemsincluding semiconductor processing equipment such as a processing toolor tools, chamber or chambers, a platform or platforms for processing,and/or specific processing components (a wafer pedestal, a gas flowsystem, etc.). These systems may be integrated with electronics forcontrolling their operation before, during, and after processing of asemiconductor wafer or substrate. In general, the electronics arereferred to as the controller, which may control various components orsubparts of the system or systems. The controller, depending on theprocessing requirements and/or the type of system, may be programmed tocontrol any of the processes disclosed herein, including the delivery ofprocessing gases, temperature settings (e.g., heating and/or cooling),pressure settings, vacuum settings, power settings, RF generatorsettings, RF matching circuit settings, frequency settings, flow ratesettings, fluid delivery settings, positional and operation settings,wafer transfers into and out of a tool and other transfer tools and/orload locks connected to or interfaced with a specific system.

Broadly speaking, the controller may be defined as electronics havingvarious integrated circuits, logic, memory, and/or software that receiveinstructions, issue instructions, control operation, enable cleaningoperations, enable endpoint measurements, and the like. The integratedcircuits may include chips in the form of firmware that store programinstructions, digital signal processors (DSPs), chips defined asapplication specific integrated circuits (ASICs), and/or one or moremicroprocessors, or microcontrollers that execute program instructions(e.g., software). Program instructions may be instructions communicatedto the controller in the form of various individual settings (or programfiles), defining operational parameters for carrying out a particularprocess on or for a semiconductor wafer or to a system. The operationalparameters may, in some embodiments, be part of a recipe defined byprocess engineers to accomplish one or more processing steps during thefabrication of one or more layers, materials (e.g., boron nitride, boroncarbide, or boron carbonitride), surfaces, circuits, and/or dies of awafer.

The controller, in some implementations, may be a part of or coupled toa computer that is integrated with, coupled to the system, otherwisenetworked to the system, or a combination thereof. For example, thecontroller may be in the “cloud” or all or a part of a fab host computersystem, which can allow for remote access of the wafer processing. Thecomputer may enable remote access to the system to monitor currentprogress of fabrication operations, examine a history of pastfabrication operations, examine trends or performance metrics from aplurality of fabrication operations, to change parameters of currentprocessing, to set processing steps to follow a current processing, orto start a new process. In some examples, a remote computer (e.g. aserver) can provide process recipes to a system over a network, whichmay include a local network or the Internet. The remote computer mayinclude a user interface that enables entry or programming of parametersand/or settings, which are then communicated to the system from theremote computer. In some examples, the controller receives instructionsin the form of data, which specify parameters for each of the processingsteps to be performed during one or more operations. It should beunderstood that the parameters may be specific to the type of process tobe performed and the type of tool that the controller is configured tointerface with or control. Thus as described above, the controller maybe distributed, such as by comprising one or more discrete controllersthat are networked together and working towards a common purpose, suchas the processes and controls described herein. An example of adistributed controller for such purposes would be one or more integratedcircuits on a chamber in communication with one or more integratedcircuits located remotely (such as at the platform level or as part of aremote computer) that combine to control a process on the chamber.

In addition to the boron-containing film deposition described herein,example systems may include a plasma etch chamber or module, adeposition chamber or module, a spin-rinse chamber or module, a metalplating chamber or module, a clean chamber or module, a bevel edge etchchamber or module, a physical vapor deposition (PVD) chamber or module,a chemical vapor deposition (CVD) chamber or module, an atomic layerdeposition (ALD) chamber or module, an atomic layer etch (ALE) chamberor module, an ion implantation chamber or module, a track chamber ormodule, and any other semiconductor processing systems that may beassociated or used in the fabrication and/or manufacturing ofsemiconductor wafers.

As noted above, depending on the process step or steps to be performedby the tool, the controller might communicate with one or more of othertool circuits or modules, other tool components, cluster tools, othertool interfaces, adjacent tools, neighboring tools, tools locatedthroughout a factory, a main computer, another controller, or tools usedin material transport that bring containers of wafers to and from toollocations and/or load ports in a semiconductor manufacturing factory.

The apparatus/process described hereinabove may be used in conjunctionwith lithographic patterning tools or processes, for example, for thefabrication or manufacture of semiconductor devices, displays, LEDs,photovoltaic panels and the like. Typically, though not necessarily,such tools/processes will be used or conducted together in a commonfabrication facility. Lithographic patterning of a film typicallyincludes some or all of the following operations, each operation enabledwith a number of possible tools: (1) application of photoresist on aworkpiece, i.e., substrate, using a spin-on or spray-on tool; (2) curingof photoresist using a hot plate or furnace or UV curing tool; (3)exposing the photoresist to visible or UV or x-ray light with a toolsuch as a wafer stepper; (4) developing the resist so as to selectivelyremove resist and thereby pattern it using a tool such as a wet bench;(5) transferring the resist pattern into an underlying film or workpieceby using a dry or plasma-assisted etching tool; and (6) removing theresist using a tool such as an RF or microwave plasma resist stripper.

Structure, Composition, and Properties of the Deposited Film

Many boron-containing films, including boron nitride, boron carbide, andboron carbonitride films, are deposited using PECVD or thermal CVDprocesses. However, the properties of such films may not have adesirable dielectric constant, step coverage, etch selectivity, chemicalstability, and thermal stability, among other properties. For example,PECVD processes in depositing a boron nitride or boron carbonitride filmmay result in films with high NH content. High NH content may adverselyimpact the mechanical properties of the film, such as the film'shardness and Young's modulus and susceptibility to etching. Also, PECVDprocesses in depositing a boron carbide or boron carbonitride film mayresult in films with a significant amount of C—C bonds, C—N bonds, orN—N bonds. A significant amount of C—C bonds, C—N bonds, or N—N bondsmay lead to inconsistent properties within the film because the film maynot have regular chemical structure. For example, an area of the filmwith more B—C and B—N bonds may perform differently than an area of thefilm with more C—C, C—N, or N—N bonds. More B—C and B—N bonds mayprovide a higher Young's modulus and different chemical reactivity(e.g., etch rate). The present disclosure relates to deposition ofboron-containing films using remote plasma CVD. The boron-containingfilm may have no or substantially no C—C bonds. Further, in someembodiments, the boron-containing film may have no or substantially noC—N bonds, and no or substantially no N—N bonds.

FIG. 5 shows a graph of a FTIR spectrum for remote plasma CVD of a boroncarbonitride film using a boron-containing precursor, carbon-containingprecursor, and remote hydrogen plasma. The boron-containing precursorincluded a borane precursor and the carbon-containing precursor includeda hydrocarbon molecule with one or more carbon-to-carbon double bonds ortriple bonds. The remote hydrogen plasma included a source gas of anitrogen-containing reactant and hydrogen gas (H₂) to produce radicalsof hydrogen and nitrogen. As shown in the FTIR spectrum in FIG. 5, B—Hbonds, B—N bonds, and B—C bonds were present in the boron carbonitridefilm. However, C—C, C—N, and N—N bonds were not present in the boroncarbonitride film. This is confirmed by the x-ray photoelectronspectroscopy (XPS) data in FIG. 6. FIG. 6 shows graphs of XPS data for B1 s, C 1 s, and N 1 s for the boron carbonitride thin film. The XPS datafor B is shows peaks at a binding energy indicative of B—C bonds. TheXPS data for C 1 s shows peaks at a binding energy indicative of B—Cbonds but not C—C bonds, C—N bonds, or C—O bonds. The XPS data for N 1 sshows peaks indicative of B—N bonds but not N—C bonds or N—O bonds.

Table 1 shows various properties of the boron carbonitride film producedby remote plasma CVD processes resulting in different boron carbonitridefilm compositions. Each boron carbonitride film has an atomicconcentration of boron that is greater than 50%. Each boron carbonitridefilm has a film density greater than 1.60 g/cm³, with the hydrogen-richremote plasma CVD process producing a denser film that is greater than1.70 g/cm³. Each boron carbonitride film has a Young's modulus greaterthan 130 GPa, with the hydrogen-rich remote plasma CVD process producinga film with a Young's modulus greater than 150 GPa. Each boroncarbonitride film has a relatively low intrinsic stress value, nothaving too much compressive stress and not having too much tensilestress. Specifically, the boron carbonitride film has an intrinsicstress value between −120 MPa and 120 MPa.

TABLE 1 Composition Film Density Refractive Stress (Atomic %) (g/cm³)Index Modulus (GPa) (MPa) B₁C_(0.37)N_(0.13)H_(0.27) 1.67 2.055 132 56B₁C_(0.32)N_(0.15)H_(0.25) 1.77 2.115 153 −113

The process conditions of the present disclosure may provide for aboron-containing film with desirable mechanical properties. Theboron-containing film may have a sufficiently high Young's modulus valuewithout an excessively high compressive or tensile intrinsic stressvalue. In some implementations, the boron-containing film may have acomposition with one or more B—C and/or B—N bonds. The boron-containingfilm may have no or substantially no C—C bonds, C—N bonds, and N—Nbonds. C—C, C—N, or N—N bonds may have an adverse impact on the Young'smodulus of the boron-containing film. In some implementations, apercentage of C—C bonds, C—N bonds, or N—N bonds in the boron-containingfilm is equal to or less than about 2%, equal to or less than about 1%,equal to or less than about 0.5%, or even 0%. In some implementations,the boron-containing film has a Young's modulus value equal to orgreater than about 130 GPa, or equal to or greater than about 150 GPa.In some implementations, the boron-containing film has an intrinsicstress value between about −120 MPa and about 120 MPa, or between about−75 MPa and about 75 MPa.

FIG. 7 shows a TEM image a boron carbonitride thin film deposited onsubstrate features using a boron-containing precursor, carbon-containingprecursor, and remote hydrogen plasma with a carrier gas. Theboron-containing precursor was a borane precursor and thecarbon-containing precursor was a hydrocarbon molecule with one or morecarbon-to-carbon double bonds or triple bonds, which were provideddownstream from the remote plasma. The remote hydrogen plasma includedhydrogen radicals and nitrogen radicals. A carrier gas was flowed withthe source gas. In some implementations, no carrier gas is flowed withthe source gas. The boron carbonitride film deposited on the substratefeatures had a step coverage of at least 95%, where the substratefeatures had a height to depth aspect ratio of 7:1.

Boron nitride, boron carbide, and boron carbonitride films can haveunique etch properties and/or selectivities. The boron nitride, boroncarbide, and boron carbonitride films may be able to etch under certainetch chemistries and resistant to etch under other etch chemistries. Insome implementations, the boron nitride, boron carbide, and boroncarbonitride film may have different etch properties depending onwhether the film has been oxidized.

The deposited film will include boron, and in some cases nitrogen,carbon, and/or one or more other elements. In some embodiments, theatomic concentration of boron is between about 30% and about 75% orbetween about 35% and about 70%. In some embodiments, the atomicconcentration of carbon is between about 10% and about 50% or betweenabout 15% and about 45%. In some embodiments, the atomic concentrationof nitrogen is between about 3% and about 25% or between about 5% andabout 20%. In all cases, the film may contain some hydrogen. However, itwill be understood that the relative atomic concentration of hydrogenwill be small. In some embodiments, the atomic concentration of hydrogenis less than about 25%, between about 2% and about 20%, or between about5% and about 15%. In one example, a boron carbonitride film containsabout 50-60% boron, about 15-25% carbon, about 5-10% nitrogen, and about5-15% hydrogen. It will be understood that the relative atomicconcentrations can vary depending on the choice of the precursors.

The boron atoms will form bonds with carbon and/or nitrogen atoms. Thecarbon atoms will not form bonds with other carbon atoms or nitrogenatoms, and the nitrogen atoms will not form bonds with other nitrogenatoms or carbon atoms. In some embodiments, the deposited film containsmore B—C bonds than B—N bonds. This can provide for a film with a lowdielectric constant. This can also provide for a film with a highYoung's modulus. In some examples, the deposited film contains a ratioof B—C bonds to B—N bonds that is between about 1:1 and 3:1. In certainembodiments, the film density is between about 1.5 and 2.5 g/cm³.

The process conditions described earlier herein can provide a filmstructure that is highly conformal. The relatively mild processconditions can minimize the degree of ion bombardment at the surface ofthe substrate so that the deposition lacks directionality. Moreover, therelatively mild process conditions can reduce the number of radicalswith high sticking coefficients that would have a tendency to stick tothe sidewalls of previously deposited layers or films. Conformality maybe calculated by comparing the average thickness of a deposited film ona bottom, sidewall, or top of a feature to the average thickness of adeposited film on a bottom, sidewall, or top of a feature. For example,conformality may be calculated by dividing the average thickness of thedeposited film on the sidewall by the average thickness of the depositedfilm at the top of the feature and multiplying it by 100 to obtain apercentage. “Features” as used herein may refer to a non-planarstructure on the substrate, typically a surface being modified in asemiconductor device fabrication operation. Examples of features includetrenches, vias, pads, pillars, domes, and the like. A feature typicallyhas an aspect ratio (depth or height to width). In certain embodiments,for features having an aspect ratio of about 2:1 or more, theboron-containing film may be deposited with a conformality between about50% and 100%, more typically between about 80% and 100%, and even moretypically between about 90% and 100%. For example, a boron carbonitridefilm on a feature between about 5:1 and about 10:1 may have aconformality of at least 95%.

The process conditions can also provide a film structure with a lowdielectric constant. The boron-containing film may be formed of amajority of B—C bonds and/or B—N bonds with a limited or no amount ofC—C bonds, C—N bonds, or N—N bonds. This can provide for improvedelectrical and mechanical properties while maintaining a relatively lowdielectric constant. In various embodiments, the boron-containing filmhas an effective dielectric constant of about 5.0 or lower, of about 4.0or lower, of about 3.5 or lower, or of about 3.0 or lower. In someembodiments, the boron-containing film has an effective dielectricconstant between about 2.0 and about 5.0.

Applications

The present disclosure may be further understood by reference to thefollowing applications for high-quality boron-containing films, whichapplications are intended to be purely illustrative. The presentdisclosure is not limited in scope by the specified applications, whichare simply illustrations of aspects of the present disclosure.

In some embodiments, a boron-containing film may be deposited overexposed copper. In some embodiments in depositing the boron-containingfilm, reaction conditions adjacent to the substrate can be free ofoxidants, such as O₂, O₃, and CO₂, including radicals thereof. Thus, theboron-containing film may be deposited directly over the exposed copperwithout oxidizing copper (e.g., creating cupric oxide). Suchboron-containing films can serve as etch stop layers, which can alsoserve as copper diffusion barriers. The presence of the boron-containingfilm can provide a sufficiently low dielectric constant with excellentleakage properties to serve as a diffusion barrier. In some embodiments,the boron-containing film can be placed in between adjacentmetallization layers that are typically produced by a damascene process.The boron-containing film can resist etching and can be sufficientlydense to minimize the diffusion of copper ions into adjacent regions ofdielectric material. The boron-containing films may serve as cappingmaterials to encapsulate copper and may have excellent adhesion tocopper or copper alloy surface.

In some embodiments as shown in FIG. 1B, a boron-containing film 111 canbe conformally deposited on features 112 of a substrate 110. Thefeatures 112 can be isolated or dense features, where the features 112can have relatively small critical dimensions (CD). In some embodiments,the features can have a CD that is equal to or less than about 20 nm,equal to or less than about 10 nm, or equal to or less than about 5 nm.The height to width aspect ratio of the features 112 can be greater than2:1, greater than 5:1, greater than 10:1, or greater than 20:1. The stepcoverage of the boron-containing film 111 deposited on the features 112is at least 80%, at least 85%, at least 90%, or at least 95%.

In some embodiments, boron-containing film may be deposited as verticalstructures adjacent to metal or semiconductor structures. Deposition ofboron nitride, boron carbide, or boron carbonitride provides excellentstep coverage along sidewalls of metal or semiconductor structures tocreate the vertical structures. In certain embodiments, the verticalstructures may be referred to as spacers or liners. Boron nitride, boroncarbide, and boron carbonitride vertical structures may serve as anashable conformal hard mask with a high modulus and low dielectricconstant. Thus, a boron-containing film may function as a low dielectricconstant spacer or liner in a variety of applications.

FIG. 1C illustrates a cross-section of boron-containing liners 121deposited on the sidewalls of a gate electrode structure of atransistor. As illustrated in FIG. 1C, the transistor can be a CMOStransistor with a silicon substrate 120 having a source 122 and a drain123. A gate dielectric 124 can be deposited over the silicon substrate120, and a gate electrode 125 can be deposited over the gate dielectric124 to form the transistor. Oxygen doped silicon carbide spacers orliners 121 can be deposited on the sidewalls of the gate electrode 125and gate dielectric 124.

In another example, FIG. 1D illustrates a cross-section ofboron-containing films deposited on sidewalls of exposed copper lines inan air gap type metallization layer. Air gaps 130 can be introduced intoan integrated circuit layer between copper lines 132 that can reduce theeffective k-value of the layer. Boron-containing liners 131 can bedeposited on the sidewalls of the copper lines 132, and a nonconformaldielectric layer 133 can be deposited on the air gaps 130, liners 131,and copper lines 132. Examples of such air gap type metallization layerscan be described in U.S. Patent Application Publication No. 2004/0232552to Fei Wang et al., which is herein incorporated by reference in itsentirety and for all purposes.

In some embodiments, an oxygen doped silicon carbide film may bedeposited on the sidewalls of patterned porous dielectric materials.Ultra low-k dielectric materials can be made from a porous structure.The pores in such materials can provide areas for ingress of metalduring deposition of subsequent layers, including the deposition ofdiffusion barriers containing a metal such as tantalum (Ta). If too muchmetal migrates into the dielectric material, the dielectric material mayprovide a short circuit between adjacent copper metallization lines.Accordingly, not only can boron-containing films serve as barrierlayers, etch stops, encapsulating layers, ashable conformal hard masks,spacers, liners, but boron-containing films can serve as pore sealants.

FIG. 1E illustrates a cross-section of boron-containing film as a poresealant for porous dielectric materials. A porous dielectric layer 142can have a plurality of trenches or vias cut into the porous dielectriclayer 142 to form pores 140. Boron-containing film 141 can be depositedalong the pores 140 to effectively seal the pores 140. Sealing the pores140 with the boron-containing film 141 can avoid damaging the porousdielectric layer 142 that may otherwise be incurred by other sealingtechniques using a plasma. The boron-containing film 141 can besufficiently dense as a pore sealant. In some embodiments, an etcheddielectric material such as the porous dielectric layer 142 may first betreated by a “k-recovery” process, which exposes the porous dielectriclayer 142 to UV radiation and a reducing agent. This recovery process isfurther described in commonly owned U.S. Patent Application PublicationNo. 2011/0111533 to Varadarajan et al., which is incorporated byreference herein in its entirety and for all purposes. In another“k-recovery” process, the porous dielectric layer 142 can be exposed toUV radiation and a chemical silylating agent. This recovery process isfurther described in commonly owned U.S. Patent Application PublicationNo. 2011/0117678 to Varadaraj an et al., which is incorporated byreference herein in its entirety and for all purposes. After exposingthe pores 140 to the recovery treatment, which makes the surface morehydrophilic and provides a monolayer of material, a layer of conformallydeposited boron-containing film 141 can be deposited to effectively sealthe pores 140 of the porous dielectric layer 142.

Conclusion

In the foregoing description, numerous specific details are set forth toprovide a thorough understanding of the presented embodiments. Thedisclosed embodiments may be practiced without some or all of thesespecific details. In other instances, well-known process operations havenot been described in detail to not unnecessarily obscure the disclosedembodiments. While the disclosed embodiments are described inconjunction with the specific embodiments, it will be understood that itis not intended to limit the disclosed embodiments.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, it will be apparent thatcertain changes and modifications may be practiced within the scope ofthe appended claims. It should be noted that there are many alternativeways of implementing the processes, systems, and apparatus of thepresent embodiments. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the embodiments arenot to be limited to the details given herein.

1. A method of depositing a boron-carbon-containing film on a substrate,the method comprising: providing a substrate in a reaction chamber;flowing a boron-containing precursor into the reaction chamber towardsthe substrate, wherein the boron-containing precursor has one or moreB—H bonds; co-flowing a carbon-containing precursor with theboron-containing precursor into the reaction chamber; generating, from ahydrogen source gas of molecular hydrogen (H₂), radicals of hydrogen ina remote plasma source that are generated upstream of theboron-containing precursor and the carbon-containing precursor; andintroducing the radicals of hydrogen into the reaction chamber andtowards the substrate prior to deposition, wherein the radicals ofhydrogen are in a ground state to react with the boron-containingprecursor and the carbon-containing precursor to form aboron-carbon-containing film on the substrate.
 2. The method of claim 1,wherein all or substantially all of the radicals of hydrogen in anenvironment adjacent to the substrate are radicals of hydrogen in theground state.
 3. The method of claim 1, wherein the boron-containingprecursor includes a borane.
 4. The method of claim 3, wherein theboron-containing precursor includes diborane, triborane, tetraborane,pentaborane, hexaborane, or decaborane.
 5. The method of claim 3,wherein the boron-containing precursor includes a borane amine complex.6. The method of claim 1, wherein the carbon-containing precursor is ahydrocarbon molecule with at least a carbon-to-carbon double bond ortriple bond.
 7. The method of claim 6, wherein the carbon-containingprecursor includes propylene, ethylene, butene, pentene, butadiene,pentadiene, hexadiene, heptadiene, toluene, benzene, acetylene, propyne,butyne, pentyne, or hexyne.
 8. The method of claim 1, wherein theboron-containing film has no C—C bonds or substantially no C—C bonds. 9.The method of claim 1, further comprising: providing anitrogen-containing reactant along with the hydrogen source gas in theremote plasma source, wherein radicals of the nitrogen-containingreactant are generated in the remote plasma source; and introducing theradicals of the nitrogen-containing reactant along with the radicals ofhydrogen into the reaction chamber and towards the substrate, whereinthe radicals of the nitrogen-containing reactant and hydrogen react withthe boron-containing precursor and the carbon-containing precursor toform a boron carbonitride (BCN) film.
 10. The method of claim 9, whereinthe BCN film has no C—C bonds or substantially no C—C bonds, no C—Nbonds or substantially no C—N bonds, and no N—N or substantially no N—Nbonds.
 11. The method of claim 9, wherein the nitrogen-containingreactant includes nitrogen (N₂) or ammonia (NH₃).
 12. The method ofclaim 1, wherein the boron-carbon-containing film has a conformality ofat least 95%.
 13. The method of claim 1, wherein theboron-carbon-containing film has a Young's modulus equal to or greaterthan about 130 GPa.
 14. The method of claim 1, wherein theboron-carbon-containing film has an effective dielectric constant equalto or less than about 4.0.
 15. The method of claim 1, whereinboron-carbon-containing film has an intrinsic stress value between about−120 MPa and about 120 MPa.
 16. The method of claim 1, wherein theboron-containing precursor has one or more B—C and/or B—N bonds.
 17. Themethod of claim 1, wherein an atomic concentration of boron in theboron-carbon-containing film is between about 30% and about 75% and anatomic concentration of carbon in the boron-carbon-containing film isbetween about 15% and about 45%.
 18. A method of depositing aboron-containing film on a substrate, the method comprising: providing asubstrate in a reaction chamber; flowing a boron-containing precursorinto the reaction chamber towards the substrate, wherein theboron-containing precursor has one or more B—H bonds; generating, from asource gas including molecular hydrogen (H₂) and a nitrogen-containingreactant, radicals of hydrogen and the nitrogen-containing reactant in aremote plasma source that are generated upstream of the boron-containingprecursor; and introducing the radicals of hydrogen and thenitrogen-containing reactant into the reaction chamber and towards thesubstrate, wherein the radicals of hydrogen are in a ground state toreact with the boron-containing precursor to form a boron-containingfilm on the substrate.
 19. The method of claim 18, further comprising:co-flowing a carbon-containing precursor with the boron-containingprecursor into the reaction chamber, wherein the radicals of hydrogen inthe ground state react with the boron-containing precursor and thecarbon-containing precursor to form the boron-containing film.